1. Field of the Invention
The present invention relates to a method for clarifying biofuels. The present invention particularly relates to clarifying biodiesel.
2. Background of the Prior Art
It is well known that as the cost of crude oil increases, numerous efforts have been made to find and develop alternative fuels, particularly fuels that have a renewable, rather than a limited, source. Considerable effort has been expended researching potential fuels from regenerable biological sources, or biofuels. Biodiesel is a diesel fuel-equivalent, processed fuel derived from biological sources (such as vegetable oils), which may be used in unmodified diesel engine vehicles.
In the context herein, biodiesel fuels include, but are not necessarily limited to, alkyl esters of a fatty acid, typically either the ethyl ester or methyl ester of a fatty acid. Thus, many biodiesel fuels may be understood to contain fatty acid methyl esters (FAME). Most biodiesel fuel is presently made by transesterification of fatty triglycerides. Biodiesel fuel may also be made from free fatty acids using an acid catalyst. There are other processes that use an ion-exchange resin catalyst. Most biodiesel fuels are made from vegetable oils, including, but not necessarily limited to rapeseed, soybean, cotton seed, corn, jotropha and the like oils. Some biodiesel is made from animal fats, including, but not limited to beef and pig tallow, chicken fat, fry grease, restaurant trap grease, fish oil, and the like. Efforts are also being made to blend FAME compounds to modify properties such as low temperature handling, for instance esters from palm and soybean oils or soybean and tallow oils (e.g. beef). The mixtures may be complex. All of these fall within the definition of biodiesel fuel herein. Non-esterified or straight vegetable oils (SVO) or straight waste vegetable oil (WVO) is not included in the definition of biodiesel fuels herein. However, biodiesel fuels as defined herein may include these non-esterified SVOs or WVOs in minor proportions (less than 50 volume %, and in another embodiment less than about 1%).
The processing of biofuels is not without problems. For example, many biofuels are less hydrophobic than similar fuels prepared using fossil feedstocks. The presence of the resulting “extra” water can cause problems with processing biofuels and biofuel feedstocks. It may be desirable in the art of preparing biofuels to remove or lessen the concentration of contaminants, especially metals, in biofuels and biofuel feedstocks visible as haze.